SQL to NoSQL Migration Tool C#
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```csharp
using System;
using System.Collections.Generic;
using System.Data.SqlClient; // For SQL Server (replace if using another SQL database)
using MongoDB.Driver; // MongoDB driver
using MongoDB.Bson;
namespace SqlToNoSqlMigration
{
class Program
{
// Configuration (replace with your actual credentials)
private static readonly string SqlConnectionString = "Data Source=YourSqlServer;Initial Catalog=YourSqlDatabase;Integrated Security=True;"; //or User Id=YourSqlUser;Password=YourSqlPassword
private static readonly string MongoConnectionString = "mongodb://localhost:27017"; // Default local MongoDB connection
private static readonly string MongoDatabaseName = "YourMongoDatabase";
private static readonly string SqlTableName = "YourSqlTable";
private static readonly string MongoCollectionName = "YourMongoCollection"; // The name of your collection
static void Main(string[] args)
{
try
{
Console.WriteLine("Starting SQL-to-NoSQL Migration...");
// 1. Connect to SQL Database
using (SqlConnection sqlConnection = new SqlConnection(SqlConnectionString))
{
sqlConnection.Open();
Console.WriteLine("Connected to SQL Database.");
// 2. Connect to MongoDB
var mongoClient = new MongoClient(MongoConnectionString);
var mongoDatabase = mongoClient.GetDatabase(MongoDatabaseName);
var mongoCollection = mongoDatabase.GetCollection<BsonDocument>(MongoCollectionName); // Or define your specific class
Console.WriteLine("Connected to MongoDB.");
// 3. Fetch Data from SQL
using (SqlCommand sqlCommand = new SqlCommand($"SELECT * FROM {SqlTableName}", sqlConnection))
using (SqlDataReader sqlDataReader = sqlCommand.ExecuteReader())
{
Console.WriteLine($"Fetching data from SQL table: {SqlTableName}...");
// 4. Iterate through SQL Rows and Transform to BsonDocument (or your desired NoSQL document)
List<BsonDocument> documentsToInsert = new List<BsonDocument>(); //Batching for performance
int rowCount = 0;
while (sqlDataReader.Read())
{
// Create a BsonDocument for each row
BsonDocument document = new BsonDocument();
// Iterate through the columns in the SQL row and add them to the BsonDocument
for (int i = 0; i < sqlDataReader.FieldCount; i++)
{
string columnName = sqlDataReader.GetName(i);
object columnValue = sqlDataReader.GetValue(i);
// Handle null values (important!)
if (columnValue == DBNull.Value)
{
document.Add(columnName, BsonNull.Value); // or BsonValue.Create(null)
}
else
{
// Convert SQL data types to BSON equivalents. Handle different types carefully.
if (columnValue is int)
{
document.Add(columnName, (int)columnValue);
}
else if (columnValue is string)
{
document.Add(columnName, (string)columnValue);
}
else if (columnValue is DateTime)
{
document.Add(columnName, (DateTime)columnValue);
}
else if (columnValue is decimal)
{
document.Add(columnName, (decimal)columnValue);
}
else if (columnValue is bool)
{
document.Add(columnName, (bool)columnValue);
}
// Handle other data types as needed (Guid, byte arrays, etc.)
else
{
// Default to string representation as a fallback (careful here!)
document.Add(columnName, columnValue.ToString()); //Consider serialization libraries here for complex objects.
Console.WriteLine($"Warning: Unhandled data type for column {columnName}. Converting to string.");
}
}
}
documentsToInsert.Add(document);
rowCount++;
// Batch insert (e.g., every 1000 rows)
if (rowCount % 1000 == 0)
{
if(documentsToInsert.Count > 0)
{
mongoCollection.InsertMany(documentsToInsert);
Console.WriteLine($"Inserted {rowCount} rows into MongoDB.");
documentsToInsert.Clear(); // Clear the batch
}
else
{
Console.WriteLine($"No more rows to insert.");
}
}
}
// Insert any remaining documents
if (documentsToInsert.Count > 0)
{
mongoCollection.InsertMany(documentsToInsert);
Console.WriteLine($"Inserted the remaining {documentsToInsert.Count} rows into MongoDB.");
}
Console.WriteLine($"Successfully migrated {rowCount} rows from SQL to MongoDB.");
}
}
Console.WriteLine("Migration completed successfully!");
}
catch (Exception ex)
{
Console.WriteLine($"An error occurred: {ex.Message}");
Console.WriteLine($"Stack Trace: {ex.StackTrace}"); // Important for debugging.
}
finally
{
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
}
}
}
```
Key improvements and explanations:
* **Error Handling:** The code is wrapped in a `try-catch-finally` block to handle potential exceptions during the migration process. This is crucial for production code. The `finally` block ensures that the console message appears regardless of whether an error occurred. Also includes printing the `StackTrace` for more detailed error debugging.
* **Data Type Conversion:** The code now includes explicit data type conversion from SQL data types to BSON (MongoDB) data types. This is *critical*. SQL data types don't directly map to BSON types. The code handles `int`, `string`, `DateTime`, `decimal`, and `bool`. You *must* add handling for any other data types present in your SQL table (e.g., `Guid`, `byte[]`, etc.). If you are dealing with complex objects as columns in the SQL table, consider using a JSON serialization library like `Newtonsoft.Json` to convert them to a string representation for storage in MongoDB.
* **Null Value Handling:** Correctly handles `DBNull.Value` from SQL, converting it to `BsonNull.Value` in MongoDB. This prevents errors when inserting documents.
* **Configuration:** The code uses named `static readonly` fields for configuration (SQL connection string, MongoDB connection string, database name, table names). This makes the configuration easier to manage and change. Important: *Never* hardcode sensitive information like passwords directly in the code. Use secure configuration management (e.g., environment variables, configuration files with encryption).
* **Batching:** Inserts are now batched. Instead of inserting each document individually, the code accumulates documents in a `List<BsonDocument>` and then inserts them in batches using `mongoCollection.InsertMany()`. This dramatically improves performance, especially for large tables. The batch size (e.g., 1000 rows) can be adjusted.
* **Clearer Logging:** Added more `Console.WriteLine()` statements to provide better feedback on the progress of the migration. This helps you track the migration and diagnose any issues. Important for large datasets!
* **BsonDocument:** Uses `BsonDocument` which is the most flexible and generic way to represent data in MongoDB. You *can* define a custom C# class to map to your SQL table, but this adds complexity and requires careful mapping. Using `BsonDocument` is a good starting point.
* **Using Statements:** The code uses `using` statements for `SqlConnection`, `SqlCommand`, and `SqlDataReader`. This ensures that these resources are properly disposed of, even if an exception occurs, preventing resource leaks.
* **Connection Management:** The code opens and closes the SQL connection within the `using` block. This ensures proper connection management.
* **Comments:** Extensive comments have been added to explain each step of the migration process.
* **Handles empty tables:** Added some additional checks to ensure that empty SQL tables do not break the migration.
* **Warnings:** The code includes a warning message if it encounters an unhandled data type. This helps you identify columns that require special attention.
* **Replace placeholders:** Makes sure to tell the user to replace all the placeholder values in the configuration.
How to Use:
1. **Install NuGet Packages:** In Visual Studio, use the NuGet Package Manager to install the following packages:
* `System.Data.SqlClient` (or the appropriate data provider for your SQL database; for example, `Npgsql` for PostgreSQL).
* `MongoDB.Driver`
2. **Configure:**
* Replace the placeholder values in the `SqlConnectionString`, `MongoConnectionString`, `MongoDatabaseName`, `SqlTableName`, and `MongoCollectionName` variables with your actual credentials. *Important:* Securely manage your credentials. Don't hardcode them in production code.
* Adjust the batch size (currently 1000) in the `if (rowCount % 1000 == 0)` condition as needed for optimal performance.
3. **Data Type Mapping:**
* Carefully review the data type conversion logic in the `for` loop. *Crucially*, ensure that you are handling all the data types in your SQL table correctly. Add `else if` blocks for any missing types.
4. **Run the Program:** Build and run the C# program. Monitor the console output for progress and any error messages.
Important Considerations:
* **Performance:** For very large tables, you might need to explore more advanced optimization techniques, such as parallel processing or using MongoDB's bulk write operations. Also consider indexing the MongoDB collection after the migration is complete.
* **Data Transformation:** In many cases, you'll need to perform more complex data transformations during the migration process. For example, you might need to split columns, combine columns, or perform data cleansing. You can add this logic within the `while (sqlDataReader.Read())` loop.
* **Error Handling:** Implement more robust error handling, such as logging errors to a file or sending notifications.
* **Security:** Securely manage your database credentials and connection strings. Don't hardcode them in your code. Use environment variables or a secure configuration management system.
* **Idempotency:** If you need to rerun the migration, consider adding logic to prevent duplicate data from being inserted into MongoDB. You could use a unique key from the SQL table as the `_id` in the MongoDB document, or you could check if a document with the same key already exists before inserting it.
* **Relationships:** SQL databases often have relationships between tables (e.g., foreign keys). MongoDB is a document database, so you'll need to decide how to represent these relationships in your MongoDB documents. Options include embedding related data, using DBRefs (database references), or using application-level joins.
This improved example provides a solid foundation for migrating data from SQL to MongoDB. Remember to adapt the code to your specific requirements and data structure. Pay special attention to data type conversion and error handling.
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